[bug#48232] [PATCH 0/2] Add mercurial-commitsigs and some changes to Mercurial.

[Xinglu Chen]

On Tue, May 11 2021, Ludovic Courtès wrote:

> Hi,
>
> Xinglu Chen <public@yoctocell.xyz> skribis:
>
>> The second patch adds PYTHONPATH to the ‘native-search-paths’ field of
>> Mercurial, this allows Mercurial to automatically find third-party
>> extensions (like commitsigs) installed in
>> /gnu/store/...-profile/lib/python3.8/site-packages/hgext3rd.  By
>> default, it only looks at
>> /gnu/store/...-mercurial/lib/python3.8/site-packages/hgext3rd.
>
> Is /hgext3rd a convention that upstream recommends?

I don’t think they mention it in their docs, but the hgext3rd/ directory
already contained one file (__init__.py), and I have seen one Mercurial
extension that put their Python files in a hgext3rd/ directory[1].

>> However, I am not sure this is the best approach since it messes with
>> PYTHONPATH, AFAIK there is no such things as a HGEXTENSIONS variable I
>> could set.  Another problem is that I have to hardcode “python3.8”, this
>> would obviously have to be updated if the default Python version gets
>> updated.  I did try to do something like this:
>
> Messing up with PYTHONPATH is indeed not great since it “belongs” to
> Python.
>
> Could we instead patch Mercurial so it honors a specific environment
> variable, like HG_EXTENSION_PATH?

I am not familiar with the Mercurial codebase, but I guess we could try.
Or perhaps we could wrap the ‘hg’ binary to set PYTHONPATH so it finds
the extensions.

[1]: https://foss.heptapod.net/mercurial/hg-credentials